The program consists of 8 projects concerned with the spinal cord. In addition, there are several shared facilities. The first 2 projects address the problem of neural regeneration as it affects the spinal cord of the rat. In the first project, the possibility that sprouting occurs following dorsal rhizotomy or hemisection of the spinal cord will be assessed using a stereological analysis of the synapses in the upper 3 laminae seen using the electron microscope. The second project will extend previous work showing that antibodies to nerve growth factor induce sprouting of dorsal root axons. Observations will be made of axonal number in the dorsal funiculus and of synaptic numbers in the dorsal horn using a stereological analysis. Project 3 will determine the destination of the unmyelinated primary afferent fibers in the dorsal and dorsolateral funiculi of the cat. Counts will be made of these fibers at the segmental level and at the C2 level on the normal side and on the side of multiple dorsal rhizotomies using the electron microscope. Projects 4 and 5 are concerned with the pain system in the monkey and rat and will examine the neurotransmitter/modulator content of synaptic contacts on identified spinothalamic tract cells, using immunocytochemistry at the light and electron microscopic levels. Emphasis in project 4 is on substance P-, enkephalin- and serotonin-containing synapses and in project 5 on catecholamine-containing synapses. Project 6 will examine the biophysical properties of interneurons in the lamprey spinal cord to determine if dynamic changes in these properties affect signal transmission. The goal of project 7 is to analyze the interneuronal circuits responsible for generating the pattern of locomotor activity in the stingray spinal cord, using a combination of anatomical and electrophysiological techniques. Project 8 investigates the reasons for the presence of immunoglobins in motoneurons of the rodent spinal cord. The shared facilities include an aquarium, a central computer facility, an electronics shop, an electron microscope facility.